Thermoresponsive circuit controller



Patented Jan.- 5, 1943 THERMOBESPONSIVE CIRCUIT CONTROLLER George M. Hausler, Ballston Lake, N. Y., assignor to General Electric Company, a corporation of New York Application February 13, 1942, Serial No. 430,770

14 Claims.

My invention relates to thermoresponsive circuit controllers and particularly to hot wire relays of the type having contacts biased toward circuit-closing position.

Hot wire relays of the normally open type ordinarily comprise a movable contact mounted upon a resilient member which is normally biased to bring the movable contact into engagement with a fixed contact, in combination with a thermally expansible member arranged to exert a tensile force upon the resilient member and to hold the contactsseparated in the deenergized or contracted position of the expansible member. With such an arrangement the expansible member is constantly under tension and, if it is broken for any reason, it .will permit the contacts to engage and remain engaged so that other apparatus may become overloaded. It will be immediatelyevident that it is highly desirable to arrange a relay so that upon mechanical failure of the hot wire the contacts will assume an open rather specification taken in conjunction with the accompanying drawing, in which Fig. 1 is a plan view of a hot wire relay embodying my invention in one form; and Fig. 2 is a plan view of a hot wire relay embodying my invention in a modified than a closed position. By a normally open relay I mean one which is in a circuit-opening position when deenergized.

Accordingly, it is an object of my invention to provide a new and improved thermoresponsive circuit controller which shall assume a circuitopening position upon failure of the thermoresponsive member.

It is a further object of my invention to provide a normally open hot wire relay biased to a circuit-closing position and arranged to assume a circuit-opening position upon mechanical failure of the hot wire.

According to my invention a relay having normally open separable switch contacts biased to a circuit-closing position is also provided with a movable member biased to a circuit-opening position. A hot wire under tension is connected to retain the movable member out of its circuitopening position under all normal operating conditions and to control circuit-opening and closing movement of the separable switch contacts.

'In the particular embodiments of my invention which I have chosen for the purpose of illustration a thermally expansible member, such as a wire, is connected under tension to a pair of movably mounted contacts, one of which is biased to a circuit-opening position with a relatively small force and the other of which is biased to a circuitclosing position with a relatively greater force.

. By this arrangement the contact biased to a circult-closing position exerts the predominant force and maintains the other contact normally in a circuit-closing position against its weaker biasing force. A fixed stop is provided to determine the circuit-closing position of the contact with the circuit-opening bias so that the contact provides a normally fixed point for the attachment of one cutter the hot wire. The opposite end of the form.

suitable insulating material upon which are mounted apair of fixed contacts II and I2 and a pair of movable contacts l3 and I4 arranged to engage the fixed contacts I I and I 2, respectively. In the particular form of the device shown, the fixed contacts H and [2 are carried upon electrically conducting strips l5 and I5 which are in turn connected to line terminal blocks l! and I8 mounted upon the base Ill. The strip I5 is rigid, at least with respect to the conducting strip I6, and may, if desired, be'dispensed with, the contact ll being rigidly mounted directly upon the base 10. The conducting strip 16 is resilient and is biased against a fixed stop .Thebase III is also provided with a pair of levenfspi'ings 25 and 26, respectively, upon the free ends of which are mounted the movable contacts l3 and 14, respectively. The opposite ends of the springs 25 and 26 are electrically connected by a jumper 26a so that the line circuit passes through the contacts l2, l4, l3 and II in series. Intermediate their ends the springs 25 and 26 .have connected thereto perforated attachment plates of insulating material 21 and 28, respectively, between which are laced any desired number of lengths of a thermally expansible wire 29. The wire 28 is fastened at its ends to the plates 21 and 28 and is provided with flexible leads 3!] and 3| for connection to a source of heating current supply. It will be understood by those skilled in the art, however, that it is not essential to the invention that the wire 29 be heated by direct conduction of an electric current, but that the wire 29, or any other thermally expansible member which may be used, may be indirectly heated by the provision of electric or other heating means proximate to the expansiblemember.

In the position of the relay shown at Fig. 1 the wire 29 is cooled and contracted so that the line circuit between the terminals I1 and I 8 is broken at the contacts l2 and M. The parts are maintained in this position by virtue of the fact that the spring 26 is biased with a relatively large force in a direction to bring'the contact l4 into engagement with the fixed contact l2, while the Referring to Fig. 1, I have shown a base In of cuit.

spring 25 is biased with a relatively small force in a direction to disengage the contact l3 from the contact II. For example, the spring 26 may be biased to the left, as viewed in Fig. 1 with the force of about ten ounces, while the spring 25 may be biased to the right, as viewed in Fig. l, with a force of about two ounces. Also, the biasing force of the resilient conducting strip l6 against the stop |6a is less than the difference between the biasing forces of the springs 25 and 26.

With the above understanding of the construction and arrangement of the various component parts If the relay shown at Fig. 1, the mode of operation of the relay as a whole will be clear from the following brief description: As previously pointed out, when the wire 29 is cooled and contracted to draw the springs 25 and 26 toward each other, the spring 26, having the greater biasing force, will draw the spring 25 to the left and bring the contacts H and I3 normally into engagement. Thus, the spring 25 is normally brought against a stop, such as the rigid fixed contact against the influence of its own relatively weak circuit-opening bias. With the wire 29 in its contracted state, its length is insuflicient to permit engagement between-the contacts l2 and I4. If now a. heating current is passed through the wire 29 the wire will expand and permit an increase in the spacing between the insulating attachment plates 21 and 28 and the contacts l3 and I4. Since the spring 25 and the contact I3 are held firmly against the rigid fixed contact H, the spring 26 and the contact M will be permitted to move to the left, as viewed in Fig. 1, under the influence of the bias of the. spring 26.

The resilient conducting strip I6 acts as a wipe spring and provides sufiicient contact pressure between the contacts l2 and I4 without producing disengagement of the contacts II and I3. It will be evident that for this purpose the force with which the spring strip is biased-,against the stop |6a must be less than the difierence between the biasing forces between the cantilever springs 25 and 28.; For example, if the biasing force of the spring strip l6 against the stop |6a is two ounces, then the ten-ounce biasing force of the cantilever spring 26 will be more than suificient to overcome the combined oppositely directed biasing forces of the spring strip l6 and the cantilever spring 25. Thus, as the contact l4 moves to the left, it moves the contact |2 with it without losing so much of its biasing force that the contacts H and |3 will become disengaged.

Assuming now that the tension wire 29 is burned by excessive current or fails mechanically for some other reason, it will be evident that the cantilever spring 26 will move' to the left under the influence of its own bias to engage the contacts l2 and i4, but that simultaneously the cantilever spring 25 will move to the right under the influence of its bias, thereby to disengage the contacts H and I3 and break the line cirnormally engages the contact with the circuit- Thus, although my hot wire relay is nor-- opening bias without the interposition of a pair of relatively fixed contacts. At Fig. 2 I have shown a base 4|] of insulating material having mounted thereon a pair of cantilever springs 4| and 42 having their free .ends juxtaposed and rovided with switch contacts 43 and 44. The spring 4| is biased to a circuit-closing position and the spring 42 is biased to a circuit-opening position. The springs 4| and 42 are mounted upon termianl blocks 45 and 46, respectively, on the base 40. The cantilever spring 42 is arranged to engage a fixed stop 41 to limit its movement in the circuit-closing direction, and the cantilever spring 4| is arranged to engage a fixed stop 48 to limit its movement in the circuit-closing direction.

Pivotally mounted upon the base 40 at a point spaced from the contacts 43 and 44, I provide a lever 49, one end of which is connected to the free end of the cantilever spring 42 by a tension member 50 and the other end of which carries a perforated insulating attachment plate 55 similar to the plates 21 and 28 of Fig. 1. Opposite the plate 55 and mounted upon the cantilever spring 4| I provide a similar insulating attachment plate 56. Between the plates 55 and 56 is threaded any desired number of lengths of a thermally expansible wire 51. As in the modification of Fig. 1, I have shown the wire 51 provided with end terminals 58 and 59 for connection to a source of heating current supply, but it will be understood by those skilled in the art that, if desired, the wire 51 may be heated from any desired source other than electric current flowing through the wire itself. As as Fig. l, the contact spring 4| having the circuit-closing bias predominates over the weaker circuit-opening bias of the contact spring 42, so that when the wire 51 is cooled and contracted, as shown at Fig. 2, the contact spring 4| exerts a tensile force upon the wire 5! tending to rotate the lever 49 in a counterclockwise,direction thereby to exert a tensile force upon the wire 5|) and to draw the contact spring 42 to the right, as viewed in Fig. 2, against the stop 41.

In operation, when the wire 51 is heated and permitted to expand the contact spring -4| will move to the left, as viewed in the drawing, while continuing to exert a circuit-closing force upon the contact spring 42. As the contact spring 4| and the contact 43 move tothe-left under the influence of the spring biasing force, the contacts 43 and 44 are brought into engagement. It will be noted that the provision of a wipe spring, such as the spring |6 of Fig. 1, is not necessary in the modification of Fig. 2. Continued movement of the contact 43 to the left after it initially engages the contact 44 has no tendency to inter rupt the circuit until such time as the contact spring 4| engages the fixed stop 48 and permits the contact spring 42 to leave the stop 41. How- 'ever, under normal current and voltage conditions, the parts are so arranged that in the circuit-closing position of the relay the contact spring 4| does not come into engagement with the stop 48.

If now the wire 51 becomes broken for any reason, the contact springs 4| and 42 are free to move under the influence of their respective biases so that the spring 4| will move against the stop 48 and the spring 42 will move to the left and away from the stop 41 sufliciently far to disengage the contact 44 from the contact 43.

It will now be evident that I have provided a normally open hot wire relay having its contacts biased to a circuit-closing position but so ar ranged that upon fracture of the thermal element the relay will assume not a circuit-closing, but rather a circuit-opening position. For this purpose I have provided a member biased to a circuit-opening position and held against its bias by the tension of an expansible wire to a position spaced from its circuit-opening position, one end of the wire being movable under the influence of a member biased to a ,circuit-closing position. In the particular forms of the invention illustrated, I have chosen to provide two contact members, one of the contact members being biased to a circuit-opening position with a small force and the other to a circuit-closing position with a large force, in combination with a hot wire under tension connected between the contact members normally to oppose the bias of both members. g

While I have illustrated certain preferred embodiments of my invention by way of illustration, many further modifications will occur to those skilled in the art, and I therefore wish to have it understood that I intend by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure bv Letters Patent of the United States is:

1. A circuit controller comprising a pair of relatively movable switch contacts, at least one of said contacts being movable between circuitopening and circuit-closing positions and being biased to its circuit-closing position, a movable member associated with said contacts and movable between circuit-opening and circuit-closing positions, said movable member being biased to a circuit-opening position, and a thermally expansible member connected to said movable member normally to retain said movable member in a position spaced from said circuitopening position, said thermally expansible member being operatively associated with said one contact normally to retain said one contact in its circuit-opening position and being arranged to control circuit-opening and circuit-closing movement of said one contact by its expansion and contraction under changing temperature conditions.

2. A circuit controller comprising a pair of relatively movable switch contacts, at least one of said contacts being movable between circuitopening and circuit-closing positions and being biased to its circuit-closing position, a thermally expansible member operatively associated with said one contact to control circuit-opening and circuit-closing movement thereof by its expansion and contraction, and a member movable between circuit-opening and circuitwlosing positions connected to said expansible member, said movable member being biased to its circuit-opening position and being retained in a position .spaced from said circuit-opening position by said thermally expansible member during normal opening and closing movements of said contacts.

3. A circuit controller comprising a pair of relatively movable switch contacts, at least one of said contacts being movable between circuitopening and circuit-closing positions and being biased to its circuit-closing posi n, a thermally expansible member operatively associated with said one contact to control circuit-opening and circuit-closing movement thereof by its expansion and contraction, and a member movable between circuit-opem'ng and circuit-closing positiopg connected to said expansible member, said 7 closing position by said thermally expansible member during normal opening and closing moveone contact controlling means upon mechanical failure of said thermally expansible means.

5. A circuit controller comprisingv a pair of relatively movable contacts, at least one of said contacts being movable between circuit-closing" and circuit-opening positions and being biased to its circuit-closing position with a predetermined force, a movable member having a circuit-closing and a circuit-opening position, said movable member being biased to its circuit-opening position with a force less than said predetermined force, and a thermally expansible tension member connected between said one contact and said movable member normally to retain said one contact in its circuit-opening position and said movable member in its circuit-closing position, whereby when subjected to changes in temperature said thermally expansible member controls the movement of said one contact between its circuit-opening and circuit-closing positions while maintaining said movable member in its circuit-closing position and mechanical failure of said thermally expansible member permits said movable member to assume its circuit-opening position.

6. A circuit controller comprising a pair of contacts movable between circuit-opening and circuit-closing positions, one of said contacts being biased to its circuit-closing position with a relatively large biasing force and the other of said contacts being biased to its circuit-opening position with a relatively small biasing force, a thermally expansible member connected between said contacts normally to oppose the bias of both of said contacts and to hold said one contact in its circuit-opening position when said member is cooled and contracted, said contact with the circuit-closing bias predominating in force to maintain closed said contact with the circuit-opening bias.

7. A circuit controller comprising a pair of contacts movable between circuit-opening and circuit-closing positions, a first of said contacts being biased to its circuit closing position with a relatively large force and a second of said contacts being biased to its circuit-opening position with a relatively small force, fixed stop means determining the closed-circuit position of said second contact, and a thermally expansible means connected between said contacts normally to oppose the bias of both said contacts and to hold said first contact in its circuit-opening position when said thermally expansible means is cooled and contracted, said first contact predominating in force to maintain closed said secmovable member being biased to its circuit-opening position and being retained in its circuitcontact between its circuit-opening and circuitclosing position while maintaining said second contact in its circuit-closing position and mechanical failure of said thermally expansible member will permit said second contact to assaid second contact against said fixed stop means and to control movement of said first contact under the influence of its predominating bias, said thermally expansible means being arranged upon mechanical failure to release said second contact for circuit-opening movement under the influence of its bias.

9. A circuit controller comprising a rigidly mounted fixed contact and a resiliently mounted fixed contact, a first resiliently mounted movable contact arranged for movement into and out of engagement with said resiliently mounted fixed contact, said first movable contact being biased into engagement with said resiliently. mounted fixed contact .with a predetermined force, a second resiliently mounted movable contact arranged for movement into and out of engagement with said rigidly mounted fixed contact, said second movable contact being biased with a force less than said predetermined force to a circuit breaking position in whichit is out 01 engagement with its associated fixed contact, and a thermally expansible wire connected between said movable contacts to oppose the bias of both said contacts thereby to hold said second fixed contact in engagement with said rigidly mounted fixed contact'and to provide a normally fixed end for said thermally expansible wire, the opposite end of said expansible wire controlling movement of said first resiliently mounted movable contact into and out of engagement with said resiliently mounted fixed contact.

10. A circuit controller comprising a pair of resiliently mounted contacts juxtaposed for mutual engagement, each of said contacts being movable from a circuit-opening to a circuitclosing position, a first of said contacts being biased with a relatively strong force towards its circuit-closing position and the second of said contacts being biased with a relatively small force toward its circuit-opening position, fixed stop means limiting the circuit-closing movement of said second contact and determining the circuit-closing position thereof, and a thermally expansible wire connected under tension between said first and second contacts normally to oppose the bias of both said contacts, whereby said first contact retains said second contact in engagement with said fixed stop means and said wire controls movement of said first contact into and out of engagement with said second contact in accordance with expansion and contraction of said wire.

11. A circuit controller comprising a pair of cantilever contact springs having their free ends in uxtaposition, a pair of contacts mounted upon aaoasa'r the free ends of said contact springs for movement into and out of engagement with each other, both of said springs being biased in the same direction and to positions in which said contacts are disengaged, that spring which is biased toward the other spring being the stronger, a tension member connected between said contact springs normally to draw the weaker of said contact springs toward a contact engaging position against its bias, and fixed stop means for limiting the movement of said weaker contact spring in the contact engaging direction, said tension means including a thermally expansible member arranged to control the movement of said first contact spring in accordance with expansion and contraction under changing temperature conditions.

12. A circuit controller comprising a pair of cantilever contact springs having their free ends in juxtaposition, a pair of contacts mounted upon the free ends of said contact springs for movement in and out of engagement with each other, a first of said springs being biased to a contact engaging position with a relatively large force and the other of said springs being biased to a contact disengaging position with a relatively small force, fixed stop means limiting the movement of both said springs in their contact engaging directions, a pivotally mounted member having opposite ends connected respectively to said contact springs by means of tension members to oppose the bias of both said springs, the

predominating force of said first spring acting to hold the other of said springs in its-contact engaging position against its bias, one of said tension members comprising a thermally expansible wire arranged when cooled and contracted to hold said first contact spring in its contact disengaging position against its bias, said wire being arranged to control movement of said first contact spring between'its contact engaging and contact disengaging positions while normally maintaining said other contact spring in its contact engaging position. v

3. A circuit controller comprising a plurality of relatively movable circuit controlling contacts, a thermally expansible tension member operatively associated with said contacts to move said contacts to a circuit-opening position upon cooling and contraction of said member, spring means for continuously applying tension to said member and for moving said contacts to a circuit-closing position upon heating and expansion of said member, and spring means connected with said tension member and arranged positively to move said contacts to a circuit-opening position upon fracture of said tension member.

14. A circuit controller comprising a pair of contacts movable between circuit-opening and circuit-closing positions, one of said contacts being biased to its circuit-closing position with a relatively large biasing force and the other of said contacts being biased to its circuit-openng position with a relatively small biasing force, a thermally expansible member operatively associated with said contacts normally to oppose the bias of both of said contacts and to hold said one contact in its circuit-opening position when said member is cooled and contracted, said contact with the circuit-closing bias predominating in force to maintain closed said contact with the circuit-opening bias.

' GEORGE M. HAUSLER. 

